1. Field of the Invention
The present invention relates to an image forming apparatus having a unit which can be pulled/pushed from/to the apparatus for allowing a user to access to an image formation section and/or a sheet transporting section in the apparatus and having a mechanism for permitting the unit to be housed.
2. Description of the Related Art
In recent years, an image forming apparatus for performing high-seed printing process has been developed. Although the printing speed of a so-called high speed apparatus (high speed machine) in standard sheet size (a landscape A4 size) was 40 to 60 sheets/minute a few years ago, it is speeded up to 100 to 120 sheets/minute.
When a sheet jam occurs in such an apparatus, a number of sheets being transported are stopped in sheet transporting paths in the apparatus. To restart printing, all of the sheets remaining in the sheet transporting paths have to be removed by a user to open the transporting paths in the apparatus. However, in a high-speed machine as described above, when a sheet jam occurs, total 5 to 10 sheets may jam at each part of the sheet transporting paths in the apparatus for the reasons such that the sheets are transported at reduced intervals for high-speed printing, the size of the apparatus is large to address high-speed printing, and the sheet transporting paths are complicated and long. Therefore, as compared with an intermediate-speed or low-speed machine, there is a tendency that the work of removing the jammed sheets is complicated. Since it increases the burden on the user, an apparatus for easily removing the jammed sheets has been requested.
To address the request, a method of unitizing a part of the apparatus and enabling the unit to be pulled from the body to largely open the sheet transporting paths when removing the remaining sheets in the apparatus has been proposed. With such a configuration, visibility and operability of the user is improved. An apparatus is also known such that a unit which can be pulled is divided into a plurality of units to address the complicated shape of the sheet transporting paths, a first unit is pulled from the body to the front side (the direction orthogonal to the sheet transporting direction), and then a second unit is pulled to the front side from the first unit (refer to, for example, Japanese Patent Laid-open No. Hei 10-143046).
The method of dividing the unit which can be pulled into a plurality of units is particularly effective to the following case. In the case where a switchback section for duplex printing exists in one of the sheet transporting paths, the sheet transporting path may be constructed so that the transported sheet is turned around in a small radius. In such a case, by pulling the first unit, the sheet transporting paths for simplex printing can be mainly opened. Further, by pulling the second unit, the sheet transporting path(s) for duplex printing including the switchback section can be opened.
As another method of pulling a plurality of units, a method of pulling the first unit to the front side from the body and pulling the second unit to a sheet evacuation side (the sheet transporting direction) or a sheet feed side (the direction opposite to the sheet transporting direction) from the body is known.
However, the method of pulling the units in two stages to the front side requires assurance of a large space on the front side so that the units can be pulled. The method of pulling the first unit to the front side and pulling the second unit to the sheet evacuation side or sheet feed side does not require a large space on the front side but requires a space on the sheet feed side or the sheet evacuation side. In many cases, a finisher is attached to the sheet evacuation side and a large-capacity sheet feeder and the like is attached on the sheet feed side. To pull the units, such peripheral apparatuses have to be moved, so that the operation is troublesome. Further, the user has to perform a work of removing sheets on the front side and, further, a work of removing sheets on the sheet evacuation side or sheet feed side. Also from the viewpoint that the user has to change his/her position, the work is troublesome. Another method is therefore considered in which the first unit is pulled in a first direction (for example, to the front side) to open a sheet transporting path in a state where a photoconductor and a developing unit are left in the body and, further, a second unit is pulled from the first unit to a second direction (for example, to the sheet evacuation side) to open the sheet transporting path in the first unit.
In such a manner, a large occupation area is not required and, moreover, sheets can be removed nearby, so that the burden on the user is lighter.
In the method of pulling the first unit to the first direction and pulling the second unit from the first unit to the second direction different from the first direction, as long as the second unit is housed in the first unit, pulling the first unit from the body and pushing back the first unit to the body causes no trouble. However, in a state that the second unit is pulled from the first unit, pushing back the first unit into the body causes trouble because the pulled second unit collides with a side face of the body. As a result, there is the possibility such that the second unit, the first unit, or the body is damaged or deformed and necessary mechanism precision cannot be assured.